In the prior art, ophthalmologic laser devices are used in all areas of the eye. For example, in laser-assisted intrastromal keratomileusis (LASIK), with the aid of a microkeratome a stromal flap having a thickness of approx. 160 μm is detached from the cornea and folded open. The material-removing laser treatment is then performed in the intrastromal tissue thereby exposed, and after the treatment the flap is folded closed. With this procedure, patients have minimal pain and a rapid recovery of sight after the operation. Alternatively, the material-removing laser treatment can be carried out in a photorefractive keratectomy (PRK) on the stromal surface, after the upper epithelial layer, which is about 50 μm thick, has been irreversibly removed from the Bowman membrane with hockey knives. In both cases, an ArF excimer laser is used for refractive correction of the cornea by ablation of tissue.
In addition, femtosecond lasers have recently been used to make incisions in the cornea (femto-LASIK). Such apparatuses are also called laser microkeratomes. In this context, photodisruption is generated in the target volume, leading to a minimal blistering in the stromal tissue. If a target spot is placed on a target spot by means of a scanner system, any desired incisions (perforations) can be introduced into the cornea. Such incisions are also called laser incisions in the following. It is known from US 2006/0155265 A1, for example, to cut the flap by means of a femtosecond laser system. The ablation of the stromal tissue required for refractive correction is then carried out in a known manner by means of an excimer laser, so that mechanical manipulation can be omitted completely. However, two laser systems are necessary.
WO 2004/105661 A1 describes using the fs laser to cut an intrastromal lenticule, which can be removed, for example, through relatively small openings with the aid of suitable tweezers or also cannulas, in order to modify the refractive properties of the cornea. Furthermore, intrastromal pockets can be prepared by this method, into which artificial inlays can be introduced for refractive correction.
What is known as laser photocoagulation is performed in the fundus of the eye for various diseases of the retina, for example detached retina. As a rule, lasers emitting continuous waves (cw) are used for this purpose. The main field of application of photocoagulation is for focussing the metabolism on the still healthy regions of the retina by obliterating diseased tissue. Photocoagulation may moreover stimulate biochemical cofactors. In the case of holes in the macula or the onset of retinal detachment, scar formation can be used to fasten the retina to the layer of the eyeball lying underneath it, the choroid membrane.
In addition to refractive correction of the cornea by laser surgery and to laser coagulation, there are laser-assisted methods for therapy of the eye lens. For example, WO 01/13838 A1 and WO 2005/070358 A1 describe the treatment of presbyopia by means of fs lasers. In this, the hardened lens is restored by suitable laser incisions or photodisruption blister fields to a state of better deformability by the capsular bag or the ciliary muscle. In principle the accommodative capacity of the lens can thus be partially regenerated.
In cataract surgery, i.e. the replacement of the clouded eye lens by an artificial intraocular lens (IOL), what is known as phacoemulsification is established as a standard method for complete removal of the pathologically cloudy lens. In this context, the capsular bag surrounding the lens and comprising an anterior and a posterior membrane is cut open (capulorhexis) from the front (anterior). The lens is then emulsified with the aid of an ultrasonic handpiece to be introduced into the lens and moved in the lens, in order subsequently to be able to remove the lens material by suction. Methods based on Er:YAG and Nd:YAG lasers are also known, for example from WO 00/27325 A1, wherein the lens is broken up with the aid of low-frequency (10-100 Hz) laser ablations or laser-induced acoustic shock waves into segments which are easier to remove by suction These ultrasound or laser methods are invasive and can only be used during a conventional surgical intervention on the opened eye.
Significantly less invasive is a method which is described, for example, in WO 2009/059251 A2, wherein both the capsulorhexis incision opening up the anterior of the capsular bag and the fragmentation of the lens are carried out by means of an fs laser navigated by means of optical coherence tomography. In the method described in US 2009/137993 A, the access opening in the cornea is additionally also cut by means of the fs laser.
What is known as aftercataract typically occurs as a side effect of cataract surgery. It is a posterior capsule opacity (PCO), which develops after a cataract operation due to a proliferation of epithelial cells remaining in the capsular bag (lens epithelial cell, LEC). For treatment of aftercataract, what is known as aftercataract capsulotomy with a Q-switched Nd:YAG laser has hitherto been the method of choice. In this case, the laser beam is focussed behind the posterior capsular bag membrane and photodisruption is generated, the pressure wave of which tears the posterior capsular bag peripherally. The optically cloudy posterior membrane is removed from the optical zone of the eye by several shots, so that the patient's vision is no longer impaired.
This destruction of the posterior capsular bag membrane can be accepted with many standard IOLs, but involves risks: In view of the mechanical stability of the eye, prolapse of the vitreous body may occur due to the destroyed capsular bag; the pressure waves during a posterior YAG laser capsulotomy may increase the probability of retinal detachment.
In view of new approaches to cataract surgery, for example the refilling of the lens capsule with gelatinous synthetic lens material described inter alia in US 2009/076602 A1, in order to re-establish a certain accommodation of the eye, an intact capsular bag is required. Posterior capsulotomy is a disadvantage in this respect. Aftercataract capsulotomy can moreover present problems because the laser radiation is applied through the implanted IOL, which may thereby become damaged. There are therefore different approaches for preventing the development of aftercataract.
One possibility for preventing aftercataract is known in particular from paediatric surgery and involves the surgical opening of the posterior capsular bag membrane. The surgical intervention is carried out from the vitreous body chamber in connection with a (at least partial) pars plana vitrectomy and is therefore too involved and associated with too many complications for normal cataract operations. In particular, the reduced stability of an opened posterior capsular bag membrane can lead to a vitreous body prolapse.
To prevent aftercataract it is moreover known, for example from IN 01996MU2006 A, to kill or suppress the growth of LECs medicinally. This can be effected, for example, by flushing the capsular bag during cataract surgery. The outlay for flushing or for introduction of the medicaments is a disadvantage in this case. An addition or alternative to this are specially shaped intraocular lenses with sharp edges, which likewise impede the growth of the epithelial cells. Such IOLs are described, for example, in US 2007/027539 A1. The limitations in designing the lens shape due to the specified sharp edges are a disadvantage of this.
A further known possibility for prophylaxis of aftercataract is to generate shock waves intraoperatively, after removal of the old lens body and before insertion of a replacement lens, by means of a metal body to be inserted into the capsular bag and irradiated with an Nd:YAG laser. In this context the beam guide equipment for the laser radiation, like the metal body, must be inserted in the form of a probe into the eye and into the capsular bag and placed manually in the immediate vicinity in front of the epithelial cell layer. The shock waves lead to a detachment of the LEC layer from the capsular bag, so that the epithelial cells can be removed by suction. The probability of the occurrence of PCO thereby decreases. As a disadvantage, however, this method requires a separate work step, which must be performed manually with great care and skill, and additional equipment.